1. Field of Invention
This invention relates to free-space micro-electro-mechanical system (MEMS) optical switches. In particular, it relates to mechanical angular alignment enhancement structures associated with free-rotating hinged micro-mirror switching elements.
2. Description of Related Art
As the demand for data-networking capacity has grown, managing optical networks at the coarse granularity of the wavelength level (OC-48 and beyond) has become increasingly critical. Optical crossconnects (OXCs) with high port-countxe2x80x94on the order of 1,000xe2x80x94are emerging as the chief candidates for achieving this end. This vision, however, imposes stringent requirements on the OXCs, chiefly in the areas of port-count and loss budget, that far outstrip available technology. Recently, free-space optical MEMS (micro-electro-mechanical systems) have begun to show promise for this application, due largely to the combined merits of free-space optics and integrated photonics.
Free-space MEMS optical switches aiming at large-scale switch fabrics have been demonstrated using various approaches. See, for example, (1) H. Toshiyoshi and H. Fujita, xe2x80x9cElectrostatic Micro Torsion Mirrors for an Optical Switch Matrix,xe2x80x9d J. Microelectromechanical Systems, vol. 5, no. 4, pp. 231-237, 1996, (2) L. Y. Lin, E. L. Goldstein, and R. W. Tkach, xe2x80x9cFree-space Micromachined Optical Switches for Optical Networking,xe2x80x9d IEEE J. Selected Topics in Quantum Electronics: Special Issue on Microoptoelectromechanical Systems (MOEMS), vol. 5, no. 1, pp. 4-9, 1999, (3) R. T. Chen, H. Nguyen, and M. C. Wu, xe2x80x9cA Low Voltage Micromachined Optical Switch by Stress-induced Bending,xe2x80x9d in 12th IEEE International Conference on Micro Electro Mechanical Systems, Orlando, Fla., Jan. 17-21, 1999, and (4) B. Behin, K. Y. Lau, and R. S. Muller, xe2x80x9cMagnetically Actuated Micromirrors for Fiber-optic Switching,xe2x80x9d in Solid-State Sensor and Actuator Workshop, Hilton Head Island, S.C., Jun. 8-11, 1998, each incorporated by reference herein in their entireties.
This work has rapidly revealed the intrinsically good optical quality of free-space interconnects, particularly in the areas of crosstalk, polarization- and wavelength-independence, and bit-rate transparency. The demonstrated switching times are also well-suited for the applications of OXCs in core-transport networks.
However, the issue of tight optical-alignment tolerances in free-space optics remains to be solved.
It is therefore an object of the invention to design micro-mirror switching elements with enhanced angular precision and repeatability so as to improve the coupling efficiency of the switch and reduce losses in optical signal intensity as a result of the switching.
This and other objects are achieved by the present invention that includes integrated mechanical angular alignment-enhancement structures that are capable of achieving better than 0.1xc2x0 micro-mirror angular precision and repeatability, thus opening the path to high port-count optical crossconnects that live within cross-office optical-loss budgets.